Homozygous combination of calpain 10 gene haplotypes is associated with type 2 diabetes mellitus in a Polish population

Objective: The polymorphisms of two genes have recently been associated with complex forms of type 2 diabetes mellitus (T2DM): calpain 10 and peroxisome proliferator-activated receptor-gamma (PPARgamma). Calpain 10 is a member of a large family of intracellular proteases. It was shown in Mexican-Americans and other populations that variants of three single nucleotide polymorphisms (SNPs), -43, -19, and -63, of this ubiquitously expressed protein influence susceptibility to T2DM. However, substantial differences were shown between ethnic groups in at risk alleles and haplotypes as well as in their attributable risk. Thus, it is important to determine the role of calpain 10 in various populations. Aim: To examine the role of calpain 10 SNPs -43, -19, and -63 in genetic susceptibility to T2DM in a Polish population. Methods: Overall, 377 individuals were examined: 229 T2DM patients and 148 control individuals. The groups were genotyped for calpain 10 SNP-43, SNP-19, and SNP-63. SNP-19 was examined by electrophoresis of the PCR product on agarose gel by size, while the restriction fragment length polymorphism (RFLP) method was used for the two other markers. Differences in allele, genotype, haplotype, and haplotype combination distribution between the groups were examined by X 2 test. Results: Distributions of alleles, genotypes, and haplotypes at three loci defined by examined SNPs were not significantly different between the groups. However, the homozygote combination of 121 haplotype was more prevalent in the T2DM group than in the controls (17.9% vs 10.1%, P = 0.039). No difference was observed in the 112/121 haplotype distribution. This heterozygous haplotype combination was associated with increased risk of T2DM in several populations. Conclusion: The results of our study suggest the association of calpain 10 121/121 haplotype combination created by SNPs -43, -19, and -63 with T2DM in a Polish population. However, we were not able to confirm the previously described role of the heterozygous 112/121 haplotype combination in susceptibility to T2DM.